From a52c915a31db041268389fa3dac0b2b3366227bb Mon Sep 17 00:00:00 2001
From: Franck Nijhof <git@frenck.dev>
Date: Wed, 22 Jan 2020 21:05:26 +0100
Subject: [PATCH] Improve cache busting (#11846)

---
 plugins/cache_buster.rb                   | 10 ++++++++++
 source/_includes/javascripts/scripts.html |  2 +-
 source/_includes/site/head.html           |  4 ++--
 3 files changed, 13 insertions(+), 3 deletions(-)
 create mode 100644 plugins/cache_buster.rb

diff --git a/plugins/cache_buster.rb b/plugins/cache_buster.rb
new file mode 100644
index 00000000000..895b39a2eeb
--- /dev/null
+++ b/plugins/cache_buster.rb
@@ -0,0 +1,10 @@
+module Jekyll
+  module CacheBuster
+    require 'digest/md5'
+    def cache_buster(file_name)
+      [file_name, '?', Digest::MD5.hexdigest(File.read(File.join('./source', file_name)))].join
+    end
+  end
+end
+
+Liquid::Template.register_filter(Jekyll::CacheBuster)
diff --git a/source/_includes/javascripts/scripts.html b/source/_includes/javascripts/scripts.html
index 4330401c789..79868bc88da 100644
--- a/source/_includes/javascripts/scripts.html
+++ b/source/_includes/javascripts/scripts.html
@@ -5,7 +5,7 @@ g.src=('https:'==location.protocol?'//ssl':'//www')+'.google-analytics.com/ga.js
 s.parentNode.insertBefore(g,s)}(document,'script'));
 </script>
 
-<script src="/javascripts/prism.js?{{ site.time | date: '%s' }}" type="text/javascript"></script>
+<script src="{{ '/javascripts/prism.js' | cache_buster }}" type="text/javascript"></script>
 
 <link rel="stylesheet" href="https://cdn.jsdelivr.net/docsearch.js/2/docsearch.min.css" />
 <script type="text/javascript" src="https://cdn.jsdelivr.net/docsearch.js/2/docsearch.min.js"></script>
diff --git a/source/_includes/site/head.html b/source/_includes/site/head.html
index 35b140ccf88..b965a92e387 100644
--- a/source/_includes/site/head.html
+++ b/source/_includes/site/head.html
@@ -28,8 +28,8 @@
     <meta name="twitter:description" content="{{ page.description | default: site.description | strip_html | truncate: 200 }}">
     <meta name="twitter:image" content="{{ page.og_image | default: "/images/default-social.png" | prepend: site.url }}">
 
-        <link href="/stylesheets/prism.css?{{ site.time | date: '%s' }}" rel="stylesheet">
-        <link href="/stylesheets/screen.css?{{ site.time | date: '%s' }}" media="screen, projection, print" rel="stylesheet">
+    <link href="{{ '/stylesheets/prism.css' | cache_buster }}" rel="stylesheet">
+    <link href="{{ '/stylesheets/screen.css' | cache_buster }}" media="screen, projection, print" rel="stylesheet">
     <link href="{{ site.subscribe_rss }}" rel="alternate" title="{{ site.title }}" type="application/atom+xml">
     <link rel='shortcut icon' href='/images/favicon.ico' />
     <link rel='icon' type='image/png' href='/images/favicon-192x192.png' sizes='192x192' />